The present technology disclosed herein relates, for example, to a communication apparatus that transmits or receives a wireless signal carrying large capacity data such as images of high resolution. The present technology relates in particular to a communication apparatus that transmits or receives a high frequency wireless signal of high directivity.
High Definition Multimedia Interface (HDMI) (registered trademark) cables are, for example, used in order to send signals for images of high resolution that are reproduced and output from reproduction apparatuses such as Blu-ray disc players, to display apparatuses such as television sets. HDMI (registered trademark) is an interface standard for digital images and audio input and output, which has been primarily developed for home appliances and AV apparatuses, and allows digital data to be sent at high speed.
Fewer cables are used today because of wireless connections established between reproduction apparatuses and display apparatuses. For example, WirelessHD (registered trademark) uses a millimeter wave frequency band of 60 GHz to achieve a sending speed of some GMbps. Accordingly, even if signals for images of high resolution which are not compressed are streamed, the images of high quality can be reproduced and it is also possible to make HDMI (registered trademark) wireless.
Millimeter waves are shorter in wavelength and travel much more straightly than microwaves, which are in widespread use in the technology of wireless local area networks (LAN). Reflection attenuates millimeter waves hard and brings considerable propagation loss, so that wireless signals have a short flying distance and fail to get to distant places. Accordingly, when wireless communication is established in accordance with the WirelessHD (registered trademark) standard, the flying distance has to be extended by applying a communication method such as the array antenna technology to at least one of transmission apparatuses and reception apparatuses, the array antenna technology taking advantage of the directivity of antennas. As a result, the arrangement and direction of transmission apparatuses and reception apparatuses are so limited that the transmission apparatuses and the reception apparatuses each face in the directivity direction in which the maximal gain is obtained while wireless signals are sent.
For example, such a communication method has been devised in which one of two communication apparatuses that have established wireless communication in accordance with the WirelessHD (registered trademark) standard outputs electronics sounds according to the wireless reception states and users check the electronic sounds to make the antenna unit of each communication apparatus face in the directivity directions in which the maximal gain is obtained while wireless signals are sent (see, for example, JP 2011-254523A).
A projector has been devised that includes a WirelessHD reception apparatus that wirelessly receives image information, a monitoring unit that monitors the reception sensitivity, and a driving unit that changes the direction of the WirelessHD reception apparatus, the projector changing the direction of the WirelessHD reception apparatus on the basis of the reception sensitivity (see, for example, JP 2011-117660A).
When stationary image display apparatuses such as television sets and projectors are used as reception apparatuses, the reception apparatuses are rarely moved while they are in use (i.e., while reproducing images). Thus, the reception apparatuses can stably keep receiving wireless signals of high directivity from transmission apparatuses if the arrangement and directions of the reception apparatuses which offer satisfactory reception characteristics are decided only once when the reception apparatuses start to be used.